Beach nursery: Least terns will soon be nesting on local beaches

Range: Breeds in spring/summer along coastal beaches and major interior rivers of North America, winters in Caribbean, Central America and Northern South America.

What to look for: A small tern with a black cap while breeding, a white forehead and a black line through the eye. Yellow bill with black tip, yellow legs and feet, light gray body and white belly.

More: For more information about nesting least terns, visit www.rookerybay.org

They like open sandy beaches, just like us.

So when least terns are nesting, humans have to be careful to leave their nests — and future generations — in peace.

"They like these open, sandy beaches that are pretty unvegetated and they put their nests right in the sand," says Beverly Anderson, research biologist at Rookery Bay National Estuarine Research Reserve.

You may have already seen areas blocked off at popular local beaches, including Delnor-Wiggins Pass in Naples, Tigertail Beach on Marco Island and nearby Sand Dollar Island, as well as Keewaydin Island in Naples Bay.

When do least terns start pairing and nesting on our beaches?

Least terns arrive in Southwest Florida in March and stay until about August when their nesting season ends, explains Anderson. They often return to beaches that they've used as nesting colonies in the past.

Once they're at the colony, it's time to find a mate. To do that, male least terns catch fish and bring them back to the potential colony area to attract females.

"I've actually watched the male swing the fish back and forth and back and forth in front of the female's beak," Anderson says, laughing. "He's advertising how successful he is as a provider to his potential mate by saying, ‘Hey honey, I've got this fish.'"

If she accepts it, he feeds her and then they'll pair up for the season.

"I've watched this happen for 15 minutes and at the end of that point there was copulation," she adds. "So there was a light at the end of the tunnel for the male."

What do least terns look like?

Least terns are the smallest terns that are found in North America, Anderson says. They're usually about nine inches long from tip of bill to tip of their tail.

Their coloring is pale gray on the back, white on the belly, and a black cap on their head when they're breeding. They have yellow bill with a black tip, yellow legs and feet, a white forehead and black line through their eye.

"A lot of our other terns have a black cap but they don't have that little line that goes through the middle of the eye, so that's a good characteristic to look for," Anderson says. "Their white forehead is another good marker."

What happens after they pair up?

Once the pair bond has formed, the future parents make a shallow scrape nest in the sand. A scrape nest is just that, a scraped out area in the sand, Anderson explains.

"It's not lined with shells, it's not lined with seaweed or anything," she says. "They just take their feet and make a little shallow depression right directly on the surface of the sand and lay their eggs."

What can people do to avoid disturbing the nests?

"With all beach-nesting birds, any kind of frequent disturbance of nesting can really threaten their survival," Anderson says. If you walk to close to the nesting site you can step on chicks or eggs because they're colored to blend in with the sand — and the nests are just small indentations in the sand.

Even just scaring the parent birds off the nest can expose the eggs or small chicks to heat or predators, Anderson adds.

"If you're walking along the beach, be aware of any posted areas and stay out or as far back from the areas as you can," she advises.

If you get close, especially with least terns, the birds might leave their nests and fly at you, she says. They're very small and they probably won't hit you, but that's a sign that you're too close.

"Just stop where you are, look down to make sure there are no eggs or chicks under foot and go back toward the water edge," she says. "Sharing the shore means staying as close to the water's edge as you can."

What happens after they lay eggs?

Least tern eggs are a pale cream color with blotches on them and they're about the size of a quail's egg, which is fairly small, Anderson says. The splotchiness helps them blend into the sand.

The eggs are laid in April or May, and they hatch after about 21 days. The young, when they hatch, already have feathers.

What do the chicks look like?

"They're adorable little fuzzballs," Anderson says. "They can't fly but they can move around and they stumble around for three or four days. They'll run around the colony, but they will stay close to the nest. ... As they get larger, they run around and they won't stay within the closed areas."

Parents go out fishing to bring back regurgitated food and then, as the chicks grow, they bring them small fish.

Eventually, the chicks fledge and leave the area to migrate south for the winter. They winter in the Caribbean, Central America and northern South America.

How many least terns are there, and are they at risk?

Least terns are a threatened species in Florida and their nesting colonies are often the same areas that are preferred by people as recreational areas, Anderson explains. Last year, there were 840 nesting pairs in four areas from the South end of Keewaydin Island down to Caxambas Critical Wildlife Area.

"The south end of Keewaydin Island supports a population of least terns but not a huge population because a lot of that has become more vegetated," she explains. "Caxambas has been very good because its a large open sandbar that's surrounded by water so it's fairly predator free. Big Marco Pass is also very important because its a big open sandy area that's fairly predator free."